Image pickup device driving method, image pickup device, and image pickup system using reset cancellation

ABSTRACT

A photoelectric convertor of a pixel is reset in a second row, which is different from a first row, among plural rows during a period in which the pixel in the first row among the plural rows is being selected as a pixel to output an optical signal. The reset of the photoelectric convertor of the pixel in the second row is canceled in a period other than a period in which an A/D converting unit converts the optical signal of the pixel in the first row into a digital signal.

BACKGROUND OF THE INVENTION

Field of the Invention

One disclosed aspect of the embodiments relates to an image pickupdevice driving method, an image pickup device, and an image pickupsystem.

Description of the Related Art

There is a known image pickup device in which a plurality of pixels arearranged in plural rows and plural columns. Hereinafter, a row on whichthe pixels are arranged is referred to as a pixel row and a column onwhich the pixels are arranged is referred to as a pixel column.

Japanese Patent Laid-Open No. 2010-219958 discloses a configuration inwhich a pixel includes a photoelectric convertor, a transfer transistor,an amplification transistor having an input node, and a resettransistor. The transfer transistor transfers a charge accumulated inthe photoelectric convertor to the input node. The reset transistorresets the charge of the input node. The image pickup device in whichthe pixels are arranged in plural rows and plural columns is described.Then, it is described to perform a shutter scan that scans the reset ofthe photoelectric convertor per pixel row and a read out scan that scansa transfer of the charge accumulated in the photoelectric convertor bythe transfer transistor per pixel row. In the shutter scan, when thereset transistor and transfer transistor are both turned on, the chargeof the photoelectric convertor is reset.

SUMMARY OF THE INVENTION

One aspect of the embodiments is made in view of a later describedproblem and one aspect is a driving method of an image pickup devicethat includes a plurality of pixels configured to be arranged in pluralrows and plural columns, respectively include a photoelectric convertorfor generating charge, and respectively output an optical signal basedon the charge, and a plurality of analog-to-digital (A/D) convertingunits configured to be respectively provided corresponding to the pluralcolumns and convert the optical signal to a digital signal. The drivingmethod includes resetting the photoelectric convertor of the pixel in asecond row, which is different from a first row, among the plural rowsduring a period in which the pixel in the first row among the pluralrows is being selected as a pixel to output the optical signal, andcanceling the reset of the photoelectric convertor of the pixel in thesecond row in a period other than the period in which the A/D convertingunit converts the optical signal of the pixel in the first row into thedigital signal.

Further features of the disclosure will become apparent from thefollowing description of exemplary embodiments (with reference to theattached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a configuration of animage pickup device.

FIG. 2 is a diagram illustrating configurations of an amplifying circuitand an A/D converting unit.

FIG. 3 is a diagram illustrating an example of a configuration of apixel.

FIG. 4 is a diagram illustrating an example of an operation of the imagepickup device.

FIG. 5 is a diagram illustrating an example of an operation of the imagepickup device.

FIG. 6 is a diagram illustrating an example of a configuration of apixel.

FIG. 7 is a diagram illustrating an example of an operation of the imagepickup device.

FIG. 8 is a diagram illustrating an example of an operation of the imagepickup device.

FIG. 9 is a diagram illustrating an example of a configuration the imagepickup system.

DESCRIPTION OF THE EMBODIMENTS

A change in a potential of a transfer control line that controls a resetof the photodiode may change a potential of the transfer control line ofa pixel from which a signal is read out. Further, in the shutter scan ofone pixel row, the timing when the reset of the photodiode is canceledand the timing when a signal of the pixel in another row is read out maymatch. In this case, the change of the potential of the transfer controlline for controlling the reset of the photodiode causes a change insignals of the pixel in another row, which is being read.

With this, there may be a problem that, due to a cancellation of a resetof a photodiode in one row, a change is caused in a signal being readout from a pixel in another row.

Embodiments described in the following relates to a technique thatreduces the change in the signal being read out from the pixel in onerow due to the cancellation of the reset of the photodiode in adifferent row.

Hereinafter, embodiments will be explained with reference to thedrawings.

First Embodiment

A configuration of an image pickup device 100 according to a firstembodiment will be described with reference to FIG. 1.

The image pickup device 100 is representatively a CMOS image sensor. Theimage pickup device 100 photoelectrically converts incident lightrepresentative of an image of an object, and outputs an electric signalacquired by the photoelectric conversion, as a digital data, to outside.The image pickup device 100 has a pixel array 110 including a pluralityof pixels 111 which are arranged in a plurality of rows and a pluralityof columns. In the following, a column of the pixels 111 is referred toas a pixel column and a row of the pixels 111 is referred to as a pixelrow. Each of the plurality of pixels 111 generates charge byphotoelectrically converting an incident light. According to the presentembodiment, in purpose of simplification, the pixels are simplyillustrated in four rows and four columns, however, the pixels may bearranged in more rows and columns. The pixel array 110 typicallyincludes tens of millions of pixels 111.

The image pickup device 100 further includes a vertical scan circuit140. The vertical scan circuit 140 supplies drive pulse signals to pixelcontrol lines 112 provided to each pixel row respectively, for eachpixel row sequentially. When the drive pulse signals are supplied to thepixel control line 112, each pixel 111 included in the correspondingpixel row outputs a signal corresponding to photoelectrically convertedcharge as a voltage signal to vertical output lines 113. According tothe present embodiment, the pixels 111 respectively output, to thevertical output lines 113, a noise signal, which is a reset level signalof the pixel 111, and an optical signal, which is a signal correspondingto the charge generated by photoelectric conversion with the noisesignal superimposed thereon. Here, in the following, when the noisesignal and optical signal output from the pixel 111 are expressedtogether, they may be referred to as a pixel signal.

To the vertical output line 113, a current source 125 is connected.

The image pickup device 100 further includes an amplifying circuit 120that amplifies the optical signal input from the pixels 111 via thevertical output line 113 and provides the signal to the A/D convertingunit 130.

The image pickup device 100 further includes ramp signal supply units170 and counters 180. The ramp signal supply unit 170 provides a rampsignal Vramp to each A/D converting unit 130 via ramp signal lines 171.The ramp signal Vramp is a signal having a potential that monotonouslychanges according to elapse of the time. The counter 180 provides acount value Cnt to each A/D converting unit 130 via count data lines181.

The image pickup device 100 further includes horizontal scan circuits150 and signal processing units 190. The horizontal scan circuit 150transfers the digital data output from the A/D converting unit 130 ofeach column to digital signal lines 191 and 192. The digital datatransferred to the digital signal lines 191 and 192 is supplied to thesignal processing units 190. According to the present embodiment,digital data corresponding to the noise signal and digital datacorresponding to the optical signal are sequentially output to thedigital signal lines 191 and 192 respectively. The signal processingunit 190 performs a CDS process for subtracting digital datacorresponding to the noise signal from the digital data corresponding tothe optical signal. With this process, the signal processing unit 190obtains digital data in which a noise element is reduced from thedigital data corresponding to the optical signal. The signal processingunit 190 outputs the digital data from which the noise element isreduced to the outside of the image pickup device 100.

The image pickup device 100 further includes a timing control unit 195that controls operation of the image pickup device 100 by providingpulse signals to each of the above described components.

FIG. 2 is a diagram illustrating detailed configurations of theamplifying circuit 120 and the A/D converting unit 130. The amplifyingcircuit 120 includes an operation amplifier 121, a capacitive elementC0, a capacitive element CF, and a switch 122. The vertical output line113 is connected to an inverting input node of the operation amplifier121 via the capacitive element C0. The inverting input node of theoperation amplifier 121 is further connected to one node of thecapacitive element CF and one node of the switch 122. The other node ofthe capacitive element CF and the other node of the switch 122 areconnected to an output node of the operation amplifier 121. To anon-inverting input node of the operation amplifier 121, a voltage VC0Ris input. The amplifying circuit 120 outputs a signal that is the signalinput from the vertical output line 113 to the inverting input node viathe capacitive element C0 amplified with a ratio of (a capacitance valueof the capacitive element C0/a capacitance value of the capacitiveelement CF).

The A/D converting unit 130 includes a switch 131, a capacitive elementSH, a comparator 132, and a memory 133. The switch 131 is provided in anelectrical path between an output node of the amplifying circuit 120 andthe capacitive element SH. The switch 131 and capacitive element SHcompose a sample-and-hold circuit.

The capacitive element SH is connected to one input node of thecomparator 132. Further, to the other input node of the comparator 132,the ramp signal line 171, which transmits a ramp signal ramp, isconnected. The switch 131 is controlled by a signal PSH output from thetiming control unit 195 illustrated in FIG. 1 and is turned on and off.

An output node of the comparator 132 is connected to the memory 133.Further, to the memory 133, the count data line 181 is connected. Withthe horizontal scan by the horizontal scan circuit 150 illustrated inFIG. 1, the memory 133 outputs digital data to the signal processingunit 190.

FIG. 3 is a diagram illustrating a configuration of the pixel 111. Thepixel 111 illustrated in FIG. 3 is one of the pixels 111 in the fourrows and four columns in the pixel array 110 illustrated in FIG. 1.

The pixel 111 includes a photodiode 114, which performs photoelectricconversion, and a plurality of transistors. The photodiode 114 is aphotoelectric conversion unit that receives an incident light andgenerates charge. The photodiode 114 is connected to an input node FD ofan amplification transistor 117 via a transfer transistor 115. The inputnode FD is also connected to a power source SVDD via a reset transistor116. A first main electrode of the amplification transistor 117 isconnected to the power source SVDD and a second main electrode of theamplification transistor 117 is connected to the vertical output line113 via a selection transistor 118. A gate electrode of the selectiontransistor 118 is connected to a row selection line, which is one of thepixel control lines 112. The row selection line transmits a signal PSEL.A gate electrode of the reset transistor 116 is connected to a resetline, which is one of the pixel control lines 112. The reset linetransmits a signal PRES. Further, a gate electrode of the transfertransistor 115 is connected to a transfer line, which is one of rowcontrol lines. The transfer line transmits a signal PTX. The verticalscan circuit 140 is a control unit that controls operation of the pixel111.

When the signal PSEL becomes a high level, to the amplificationtransistor 117, current is applied by the current source 125 via thevertical output line 113 and selection transistor 118. The period thatthe current flows to the amplification transistor 117 is a period that asignal is read out from the pixel 111 to the vertical output line 113.

Here, the signal PRES, signal PTX, signal PSEL may be expressed with (m)attached. This represents that the signal is output from the verticalscan circuit 140 to the pixel 111 in “m”th row.

FIG. 4 is a timing diagram illustrating an operation in the image pickupdevice according to the present embodiment.

FIG. 4 is a diagram illustrating signals, which are output from thevertical scan circuit 140 to the respective pixels 111 in “m−1”th raw asa first line and pixels 111 in “m”th row as a second row, the signalsPSH, and a ramp signal ramp.

At time t0, the vertical scan circuit 140 sets the signal PSEL(m−1)High. With this, by the current source 125, current is flown to theamplification transistor 117 of the pixel 111 in the “m−1”th row via thevertical output line 113 and the selection transistor 118 in the “m−1”throw. Accordingly, the amplification transistor 117, power source voltageSVDD, and current source 125 compose a source follower circuit. Further,the vertical scan circuit 140 sets the signal PRES(m−1) High. With this,the potential of the input node FD of the pixel 111 in the “m−1”th rowis reset. The period that the signal PSEL(m−1) is High from time t0 totime t9 is a period that the pixels 111 in the “m−1”th row as the firstrow are selected as the pixels 111 of the pixel row to which an opticalsignal is output in the read out scan.

At time t1, the vertical scan circuit 140 sets the signal PRES(m−1) Low.With this, the reset of the input node FD is canceled. With thisconfiguration, the amplification transistor 117 of the pixel 111 in the“m−1”th row outputs a noise signal to the vertical output line 113 viathe selection transistor 118.

At the timing when the noise signal is output, the timing control unit195 turns off the switch 122. Accordingly, the noise signal is clampedin the capacitive element C0.

To the comparator 132, an offset signal of the operation amplifier 121is input.

At time t2, the ramp signal supply unit 170 starts the change ofpotential of the ramp signal ramp according to the elapse of time.Further, the counter 180 starts to count clock signals. With this, thecount signal output from the counter 180 increases its signal valueaccording to the elapse of time. When the magnitude relationship betweenthe potentials of the offset signal and ramp signal ramp changes, thesignal level of the comparison result signal output from the comparator132 changes. The memory 133 maintains a count signal at the timing whenthe signal level of the comparison result signal changes. The countsignal maintained by the memory 133 is a digital signal corresponding tothe offset signal. This digital signal will be referred to as a digitalN signal.

At time t3, the ramp signal supply unit 170 ends the change of thepotential of the ramp signal according to the elapse of time. Further,the counter 180 also ends counting the clock signals.

The period that the potential of the ramp signal ramp changes from timet2 to time t3 is a period of AD conversion of the offset signals. ThisAD conversion period may be referred to as an NAD period.

At time t4, the vertical scan circuit 140 sets the signal PTX(m−1) High.This turns on the transfer transistor 115. Accordingly, the chargegenerated by the photodiode 114 of the pixel 111 in the “m−1”th row istransferred to the input node FD.

At time t5, the vertical scan circuit 140 sets the signal PTX(m−1) Low.This turns off the transfer transistor 115. Accordingly, the transfer ofthe charge generated by the photodiode 114 to the input node FD ends.The amplification transistor 117 outputs a signal based on the chargegenerated by the photodiode 114 to the vertical output line 113 via theselection transistor 118. This signal will be referred to as an opticalsignal.

The capacitive element C0 continuously clamps the noise signals. Thus,to the operation amplifier 121, a signal in which a noise signal issubtracted from an optical signal is input. This signal will be referredto as an S signal.

The operation amplifier 121 outputs, to the comparator 132, a signalthat the S signal is amplified. This signal will be referred to as anamplified S signal.

At time t6, the ramp signal supply unit 170 starts to change thepotential of the ramp signals ramp according to the elapse of time.Further, the counter 180 starts to count the clock signals. With this,the signal value of the count signal output from the counter 180increases according to the elapse of time. When the magnituderelationship between the potentials of the amplified S signal and rampsignal ramp changes, the signal level of the comparison result signaloutput from the comparator 132 changes. The memory 133 maintains thecount signal at the timing when the signal level of the comparisonresult signal changes. The count signal maintained by the memory 133 isa digital signal corresponding to the amplified S signal. This digitalsignal will be referred to as a digital S+N signal.

At time t7, the ramp signal supply unit 170 ends changing the potentialof the ramp signal according to the elapse of time. Further, the counter180 also ends counting the clock signals.

The period that the potential of the ramp signal ramp changes from timet6 to time t7 is a period of AD conversion of the amplified S signal.This AD conversion period may be referred to as an SAD period.

After that, the horizontal scan circuit 150 performs control to outputthe digital S+N signal and digital N signal maintained in the memory 133in each column to the signal processing unit 190 sequentially from thememory 133 in each column.

During the SAD period, the vertical scan circuit 140 sets both of thesignal PRES(m) and the signal PTX(m) to be output to the pixel 111 inthe “m”th row High. During the period that the signal PRES(m) is High,when the signal PTX(m) becomes High, the charge of the photodiode 114 isreset. The operation of resetting the charge of the photodiode 114 isreferred to as an electronic shutter operation. The electronic shutteroperation performed on the plural of pixel rows sequentially for eachrow by the vertical scan circuit 140 is a shutter scan.

In the image pickup device according to the present embodiment, thecancellation of the reset of the photodiode 114 of the pixel 111 whichis different from the pixel 111 to which the optical signal based on theamplified S signal which is AD-converted during the SAD period is outputis set in a period, which is not a period of the SAD period, after theSAD period.

It is assumed that cancellation of resetting the photodiode 114 is setduring the SAD period. As the signal PTX(m) shifts from High to Low, achange occurs in the power source of a circuit, in the vertical scancircuit 140, which generates the low-level signal PTX. Due to thischange in the power source, a change occurs in low-level potential ofsignals PTX(m−1) of the pixels 111 in the “m−1”th row, which share thepower source. Due to a coupling capacity existing between the transferline that transfers the signal PTX(m−1) and the input node FD, thepotential of the input node FD changes corresponding to the change ofthe potential in the transfer line. With this, the signal level of theoptical signal changes. Due to the change of the signal level of theoptical signal, the signal level of the amplified S signal also changes.Thus, by canceling the reset of the photodiode 114 of another pixel 111during the SAD period, the signal level of the digital S+N signalchanges.

According to the present embodiment, cancellation of the reset of thephotodiode 114 of the pixel 111 which is different from the pixel 111from which the optical signal is being read is executed in a periodother than the period of the AD conversion of the signals based on theoptical signal. With this, the image pickup device according to thepresent embodiment has an effect that can suppress the change in digitalS+N signal due to the cancellation of the reset of the photodiode 114.

The operation of reading the noise signal and optical signal of thepixel 111 in the “m−1”th row is the same as that of the pixel 111 in the“m”th row. The start of a period for storing the charge of thephotodiode 114 of the pixel 111 in the “m−1”th row is at the timing oftime t8 when the signal PTX(m−1) becomes Low while the signal PRES(m−1)is High. Further, the end of the period of storing the charge of thephotodiode 114 of the pixel 111 in the “m−1”th row is at the timing oftime t14 when the signal PTX(m−1) becomes Low while the signal PRES(m−1)is Low.

Here, according to the present embodiment, the pixel 111 from which theoptical signal is being read and the pixel 111 in which the reset of thephotodiode 114 is canceled are placed next to each other. The presentembodiment is not limited to the above example and there may be pixels111 in a plurality of rows between the pixel 111 from which the opticalsignal is being read and the pixel 111 in which the reset of thephotodiode 114 is canceled, according to the setting of the length ofthe period for storing the charge.

Here, the present embodiment has explained an example that the pixel 111includes the selection transistor 118; however, the present embodimentis not limited to this example. As a substitute for the pixel 111including the selection transistor 118, the selected state andnon-selected state of the pixel 111 may be switched by the potential ofthe input node FD. For example, the power source voltage SVDD thatsupplies power to the reset transistor 116 can be made to be switchablebetween a potential for the non-selected state of the pixel 111 and apotential for the selected state of the pixel 111. For the pixel 111from which the optical signal is read out, the potential of the powersource voltage SVDD is set as the potential for the selected state.Then, the reset transistor 116 is turned on and the potential of theinput node FD is set as a potential for the selected state so that theamplification transistor 117 is turned on. On the other hand, for thepixel 111 from which the optical signal is not read out, the potentialof the power source voltage SVDD is set as the potential for thenon-selected state. Then, the reset transistor 116 is turned on and thepotential of the input node FD is set as potential for the non-selectedstate so that the amplification transistor 117 is turned off. With this,even when the pixel 111 does not include the selection transistor 118,the selected state or the non-selected state of the pixel 111 can beperformed. In the case of the pixel 111 having the above configuration,the operation according to the present embodiment can also be applied.

Second Embodiment

An image pickup device according to the present embodiment will bedescribed focusing on the difference from the first embodiment.

According to the first embodiment, the noise signal of the pixel 111 inthe “m”th row is read after the SAD period of the pixel 111 in the“m−1”th row. According to the present embodiment, during an SAD periodof the pixel 111 from which an optical signal is being read, a noisesignal of another pixel 111 is read. Then, a cancellation of a reset ofthe photodiode 114 is performed after the capacitive element SHmaintains an amplified S signal, which is in a period other than theperiod that the capacitive element SH samples the amplified S signal.

The configuration of the image pickup device according to the presentembodiment is the same as the configuration of the image pickup deviceaccording to the first embodiment.

FIG. 5 is a timing diagram illustrating an operation of the image pickupdevice according to the present embodiment. The parts different fromFIG. 4 will be mainly described.

In the operation illustrated in FIG. 4, the signal PSH is kept High.According to the present embodiment, the signal PSH shifts from Low,High, and then Low prior to the NAD period and SAD period respectively.

At time t21, the operation amplifier 121 outputs an offset signal. Attime t22, the timing control unit 195 sets the signal PSH High. Withthis, the capacitive element SH samples the offset signal. Then, at timet22, the timing control unit 195 sets the signal PSH Low. With this, thecapacitive element SH maintains an offset signal.

At time t22, the ramp signal supply unit 170 starts to change thepotential of the ramp signal ramp according to the elapse of time.Further, the counter 180 starts to count clock signals. With this, thesignal value of the count signal output from the counter 180 increasesaccording to the elapse of time. The offset signal output to thecomparator 132 in this NAD period is a signal maintained by thecapacitive element SH. When the magnitude relationship between thepotentials of the offset signal and ramp signal ramp changes, the signallevel of the comparison result signal output from the comparator 132changes. The memory 133 maintains the count signal at a timing when thesignal level of the comparison result signal changes, as a digital Nsignal.

Further, at time t23 during the NAD period, the vertical scan circuit140 sets the signal PTX(m−1) High.

After that, at time t26, the vertical scan circuit 140 sets the signalPTX(m−1) Low. With this, the amplification transistor 117 of the pixel111 in the “m−1”th row outputs an optical signal to the vertical outputline 113 via the selection transistor 118.

At time t24, the timing control unit 195 sets the signal PSH High.

In the period from time t26 to time t27, the capacitive element SHsamples the amplified S signal. Then, at time t27, the timing controlunit 195 sets the signal PSH Low. With this, the capacitive element SHmaintains the amplified S signal.

At time t27, the ramp signal supply unit 170 starts to change thepotential of the ramp signal ramp according to the elapse of time.Further, the counter 180 starts to count the clock signals. With this,the signal value of the count signal output from the counter 180increases according to the elapse of time. When the magnituderelationship between the potentials of the amplified S signal and rampsignal ramp changes, the signal level of the comparison result signaloutput from the comparator 132 changes. The memory 133 maintains thecount signal at the timing when the signal level of the comparisonresult signal changes, as a digital S+N signal.

In the SAD period from time t27 to time t30, the vertical scan circuit140 reads out the noise signal of the pixel 111 in the “m”th row to thevertical output line 113. At time t29, the vertical scan circuit 140sets the signal PSEL(m) output to the pixel 111 in the “m”th row High.Further, at time t30 during the SAD period, the vertical scan circuit140 sets the signal PRES(m) Low. With this, to the vertical output line113, the noise signal is output from the amplification transistor 117 ofthe pixel 111 in the “m”th row.

The vertical scan circuit 140 sets the signal PTX(m) output to the pixel111 which is different from the pixel 111 from which the optical signalis being read to be High at time t23. Since the signal PRES(m) is alsoset to be High, the charge of the photodiode 114 of the pixel 111 in the“m”th row is reset.

Then, at time t28, the vertical scan circuit 140 sets the signal PTX(m)output to the pixel 111 which is different from the pixel 111 from whichthe optical signal is being read to be Low. With this, at time t28, thereset of the photodiode 114 of the pixel 111 in the “m”th row iscanceled.

The image pickup device according to the present embodiment sets thecancellation of the reset of the photodiode 114 of the pixel 111 whichis different from the pixel 111 corresponding to the amplified S signal,which is AD-converted in the SAD period, in a period other than theperiod in which the capacitive element SH samples the amplified Ssignal. In an example of the present embodiment, the cancellation of thereset of the photodiode 114 is set at the timing after the capacitiveelement SH maintains the amplified S signal.

It is assumed that the cancellation of the reset of the photodiode 114is set during the period that the capacitive element SH samples theamplified S signal. As described in the first embodiment, since thesignal PTX(m) changes from High to Low, the potential of the input nodeFD of the pixel 111 from which the optical signal is being read changes.With this, the signal level of the optical signal changes. According tothe change of the signal level of the optical signal, the signal levelof the amplified S signal also changes. This changed amplified S signalis to be maintained in the capacitive element SH. Thus, in the periodthat the capacitive element SH samples the amplified S signals, due tothe cancellation of the reset of the photodiode 114 of the differentpixel 111, the signal level of the digital S+N signal changes.

According to the present embodiment, cancellation of the reset of thephotodiode 114 of the pixel 111 which is different from the pixel 111from which the optical signal is being read is performed in a periodother than the period that the capacitive element SH samples theamplified S signal. With this, the image pickup device of the presentembodiment has an effect that the changes of the digital S+N signal dueto the cancellation of the reset of the photodiode 114 can besuppressed.

Third Embodiment

An image pickup device according to the present embodiment will bedescribed focusing on a part different from the first embodiment.

The image pickup device according to the present embodiment includes apixel 1110 illustrated in FIG. 6 as a substitute for the pixel 111illustrated in FIG. 1.

The pixel 1110 of FIG. 6 includes a couple of photodiodes 114A and 114Bthat perform photoelectric conversion respectively. Further, the pixel1110 includes transfer transistors 115A and 115B. The input node FD isconnected to the photodiode 114A via the transfer transistor 115A.Further, the input node FD is connected to the photodiode 114B via thetransfer transistor 115B.

Further, the pixel 1110 further includes a micro lens 119. Thephotodiode 114A and photodiode 114B share the single micro lens 119. Thelight transmitted through the single micro lens 119 enters thephotodiode 114A and photodiode 114B.

The gate electrode of the transfer transistor 115A is connected to thetransfer line that transfers the signal PTXA(m), among the pixel controllines 112. Further, the gate electrode of the transfer transistor 115Bis connected to the transfer line that transfers the signal PTXB(m),among the pixel control lines 112.

In the pixel 1110 of FIG. 6, the two photodiodes 114A and 114B share thesingle amplification transistor 117, single reset transistor 116, andsingle selection transistor 118. With this, the number of transistorsprovided to one photodiode can be reduced.

The configuration of other parts of the image pickup device according tothe present embodiment is the same as the configuration of the imagepickup device according to the first embodiment.

FIG. 7 is a timing diagram illustrating an operation of the image pickupdevice according to the present embodiment.

The operations from time t40 to time t43 are the same as the operationsfrom time t0 to time t3 of FIG. 4 in the first embodiment.

At time t44, the vertical scan circuit 140 sets the signal PTXA(m−1)High. With this, a charge generated by the photodiode 114A of the pixel1110 in the “m−1”th row is transferred to the input node FD. At timet45, the vertical scan circuit 140 sets the signal PTXA(m−1) Low. Withthis, the transfer of the charge generated by the photodiode 114A of thepixel 1110 in the “m−1”th row to the input node FD ends. With this, theamplification transistor 117 of the pixel 1110 in the “m−1”th rowoutputs a signal based on the charge generated by the photodiode 114A tothe vertical output line 113 via the selection transistor 118. Thissignal is expressed as a pixel A signal. The pixel A signal is one ofthe optical signals output from the pixel 1110. Another of the opticalsignals is a later described pixel A+B signal.

To the operation amplifier 121, a signal, in which the noise signal thatthe capacitive element C0 clamps is subtracted from the pixel A signal,is input. This signal is expressed as an A signal.

The operation amplifier 121 outputs a signal, in which the A signal isamplified, to the comparator 132. This signal is expressed as anamplified A signal.

In the period from time t46 to time t47, the amplified A signal isAD-converted. This period is referred to as an S(A)AD period. Thedigital signal, which is maintained by the memory 133 by AD conversion,corresponding to the amplified A signal is referred to as a digital A+Nsignal.

At time t48, the vertical scan circuit 140 sets the signal PTXA(m−1) andsignal PTXB(m−1) High, respectively. With this, the charges respectivelygenerated in the photodiode 114A and photodiode 114B are transferred tothe input node FD.

At time t49, the vertical scan circuit 140 sets the signal PTXA(m−1) andsignal PTXB(m−1) Low, respectively. With this, the transfer of thecharges respectively generated in the photodiode 114A and photodiode114B to the input node FD ends. In the input node FD, the chargegenerated by the photodiode 114A during a period from time t46 to timet49 and the charge generated by the photodiode 114B are added to thecharge of the photodiode 114A which has been already transferred at timet45. With this, the amplification transistor 117 of the pixel 1110 inthe “m−1”th row outputs a signal based on the charges generated by thephotodiode 114A and photodiode 114B to the vertical output line 113 viathe selection transistor 118. This signal is referred to as a pixel A+Bsignal. The pixel A+B signal is one of the optical signals output fromthe pixel 1110 as described above.

To the operation amplifier 121, a signal in which a noise signal thatthe capacitive element C0 clamps is subtracted from the pixel A+B signalis input. This signal is referred to as an A+B signal.

The operation amplifier 121 outputs an amplified signal of the A+Bsignal to the comparator 132. This signal is referred to as an amplifiedA+B signal.

In a period from time t50 to time t51, the amplified A+B signal isAD-converted. This period is referred to as an S(A+B)AD period. Thedigital signal, which is maintained by the memory 133 by the ADconversion, corresponding to the amplified A+B signal is referred to asa digital A+B+N signal.

After that, the horizontal scan circuit 150 sequentially outputs thedigital A+N signal, digital A+B+N signal, and digital N signalmaintained in the memories 133 in each column to the signal processingunit 190 from the memories 133 in each column.

The signal processing unit 190 outputs a signal in which a digital Nsignal is subtracted from the digital A+N signal to the outside of theimage pickup device. This signal is referred to as a digital A signal.Further, the signal processing unit 190 outputs a signal in which adigital N signal is subtracted from the digital A+B+N signal to theoutside of the image pickup device. This signal is referred to as adigital A+B signal. Outside the image pickup device, a process forsubtracting a digital A signal from a digital A+B signal and obtaining adigital B signal is performed. With the digital A signal and digital Bsignal, a focus detecting operation of a phase difference detectingmethod is performed. Further, outside the image pickup device, an imageis generated from the digital A+B signal.

The vertical scan circuit 140 performs a cancellation of the resets ofthe photodiode 114A and photodiode 114B of the pixel 1110 in the “m”throw at time t52 after the S(A+B)AD period.

In the S(A+B)AD period, when a cancellation of the resets of thephotodiode 114A and photodiode 114B of the pixel 1110 in the “m”th rowis performed, a change occurs in the amplified A+B signal by themechanism described in the first embodiment. Accordingly, a changeoccurs in the digital A+B+N signal.

On the other hand, according to the present embodiment, the cancellationof the resets of the photodiodes 114A and 114B of the pixel 1110different from the pixel 1110 that is performing AD conversion isperformed in a period other than the S(A+B)AD period. With this, thechange of the digital A+B+N signal due to the cancellation of the resetsof the photodiodes 114A and 114B can be suppressed.

Here, according to the present embodiment, the vertical scan circuit 140performs a cancellation of the resets of the photodiode 114A andphotodiode 114B of the pixel 1110 in the “m”th row is performed at timet52 after the S(A+B)AD period. This example does not set any limitationas long as the cancellation of the resets of the photodiode 114A andphotodiode 114B in the pixel 1110 in the “m”th row is performed in aperiod other than the S(A+B)AD period.

Further, the vertical scan circuit 140 may perform cancellation of theresets of the photodiode 114A and photodiode 114B of the pixel 1110 inthe “m”th row in a period from time t47 to time t50, which is a periodother than the S(A)AD period. In this case, changes in the digital A+Nsignal due to the cancellation of the resets of the photodiodes 114A and114B can be suppressed.

According to a preferable example of the embodiment, the cancellation ofthe resets of the photodiode 114A and photodiode 114B is performed in aperiod other than the S(A) period and S(A+B) period. With this, a changein the signals of both digital A+N signal and digital A+B+N signal dueto the cancellation of the resets of the photodiodes 114A and 114B canbe suppressed.

On the other hand, there may be a case that it is difficult to perform acancellation of the resets of the photodiode 114A and photodiode 114B ina period other than the S(A) period and S(A+B) period, depending on thelength of the charge accumulating period. In such a case, it ispreferable that the cancellation of the resets of the photodiode 114Aand photodiode 114B is performed avoiding the S(A+B) period rather thanthe S(A) period. This is because that the signals are used in differentpurposes, which means that the digital A+B signal is used to generatedan image while the digital A signal is used to detect a focus. Anallowable range of the accuracy of the signals used to detect a focus iswider than an allowable range of the accuracy of the signals used forthe images. Thus, changes in the signals caused by a cancellation of theresets of the photodiodes 114A and 114B are easily allowed in thedigital A+N signals compared to the digital A+B+N signal. Thus, thecancellation of the resets of the photodiodes 114A and 114B may beperformed in the S(A)AD period, which is a period other than theS(A+B)AD period, depending on the setting of the length of the chargeaccumulating period.

Further, the cancellation of the resets of the photodiode 114A andphotodiode 114B may be performed at the same timing when the transfer ofthe charge from the photodiode 114A of the pixel 111 corresponding tothe amplified A+B signal being AD-converted to the input node FD isended. In other words, at time t45 in the timing diagram of FIG. 7, thesignal PTXA(m) and signal PTXB(m) may be switched from High to Low.

Further, the cancellation of the resets of the photodiode 114A andphotodiode 114B may be performed at the timing when the transfer of thecharge from the photodiode 114B of the pixel 111 corresponding to theamplified A+B signal being AD converted to the input node FD is ended.In other words, at time t49 in the timing diagram of FIG. 7, the signalPTXA(m) and signal PTXB(m) may be switched from High to Low.

Here, it is preferable that the signal PTXA(m) and signal PTXB(m) areswitched from High to Low at time t45, rather than time t49. Compared totime t49, when the signal PTXA(m) and signal PTXB(m) are switched fromHigh to Low at time t45, the change is less likely to occur in theamplified A+B signals. Accordingly, compared to time t49, when thesignal PTXA(m) and signal PTXB(m) are switched from High to Low at timet45, the change in the digital A+B+N signal is reduced. With this,compared to the digital A+N signal, the change in the digital A+B+Nsignal that does not easily allow the change in signal can be reduced.

Further, according to the present embodiment, the signal PSH is keptHigh. The operations of the present embodiment and the second embodimentmay be combined and, specifically, operation of FIG. 8 may be executed.

In the operation, the cancellation of the resets of the photodiodes 114Aand 114B in the “m”th row is performed at a timing after the capacitiveelement SH maintains the amplified A+B signal, which is a period otherthan the period that the capacitive element SH samples the amplified A+Bsignals. With this, as described in the present embodiment, changes inthe digital A+B+N signal due to cancellation of the resets of thephotodiodes 114A and 114B in the “m”th row can be suppressed. Also inthis example, the cancellation of the resets of the photodiodes 114A and114B in the “m”th row may be performed after the capacitive element SHmaintains the amplified A signal. Further, the cancellation of theresets of the photodiodes 114A and 114B in the “m”th row may beperformed in a period other than the period that the capacitive elementSH samples the amplified A+B signal, that is, in the period that thecapacitive element SH samples amplified A signal.

In the operation in FIG. 8, the cancellation of the resets of thephotodiode 114A and photodiode 114B may be performed at the same timingwhen the transfer of the charge from the photodiode 114A of the pixel111 corresponding to the amplified A+B signal being AD-converted to theinput node FD is ended.

In the operation in FIG. 8, the cancellation of the resets of thephotodiode 114A and photodiode 114B may be performed at the same timingwhen the transfer of the charge from the photodiode 114B of the pixel111 corresponding to the amplified A+B signal being AD-converted to theinput node FD is ended.

Fourth Embodiment

The present embodiment relates to an image pickup system including theimage pickup device according to the above described embodiments.

As the image pickup system, there may be a digital still camera, adigital camcorder, a monitoring camera, and the like. FIG. 9 illustratesa schematic view in a case that the image pickup device is applied to adigital still camera as an example of the image pickup system.

The image pickup system illustrated in FIG. 9 includes a barrier 1501for protecting a lens, a lens 1502 for forming an optical image of anobject on an image pickup device 1504, and a diaphragm 1503 for makingan amount of light transferring through the lens 1502 variable. The lens1502 and diaphragm 1503 serve as an optical system for collecting lightto the image pickup device 1504. Further, the image pickup systemexemplified in FIG. 9 includes an output signal processing unit 1505 forperforming a process of an output signal output from the image pickupdevice 1504. The output signal processing unit 1505 performs anoperation for performing various correction and compression according toneed and outputting the signal.

The image pickup system exemplified in FIG. 9 further includes a buffermemory unit 1506 for temporarily storing image data and an externalinterface unit 1507 for communicating with an external computer or thelike. Further, the image pickup system includes a detachable recordingmedium 1509 such as a semiconductor memory for recording or readingimage pickup data and a recording medium control interface unit 1508 forrecording and reading to the recording medium 1509. Further, the imagepickup system includes an overall control calculation unit 1510 forcontrolling various calculations and the entire digital still camera anda timing supply unit 1511 for outputting various timing signals to theimage pickup device 1504 and output signal processing unit 1505. Here,the timing signal or the like may be input from outside and the imagepickup system needs to include at least the image pickup device 1504 andthe output signal processing unit 1505 for processing the output signaloutput from the image pickup device 1504.

Further, as described in the third embodiment, the output signalprocessing unit 1505 may perform the focus detecting operation using thedigital A signal and digital B signal. Further, the output signalprocessing unit 1505 may generate an image using the digital A+B signal.Further, the output signal processing unit 1505 may perform a focusdetecting operation and an image generation.

As described above, in the image pickup system according to the presentembodiment, the image pickup device 1504 can be applied and an imagepickup operation can be performed.

Here, all of the above embodiments exemplify concrete examples toimplement the disclosure and the technical scope of the disclosureshould not be limitedly understood based on the embodiments. In otherwords, the disclosure can be implemented in various manners within thetechnological thought and its main characteristics. Further, thedisclosure may be implemented with various combinations of the abovedescribed embodiments.

With the disclosed embodiments, changes caused by cancellation of areset of a photodiode in one row can be reduced in signals being readfrom a pixel in another row.

While the disclosure has been described with reference to exemplaryembodiments, it is to be understood that the disclosure is not limitedto the disclosed exemplary embodiments. The scope of the followingclaims is to be accorded the broadest interpretation so as to encompassall such modifications and equivalent structures and functions.

This application claims the benefit of Japanese Patent Application No.2015-242314, filed Dec. 11, 2015, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. A driving method of an image pickup device that comprises a plurality of pixels configured to be arranged in plural rows and plural columns, respectively include a photoelectric convertor for generating charge, and respectively output an optical signal based on the charge, and a plurality of A/D converting units configured to be respectively provided corresponding to the plural columns and convert the optical signal to a digital signal, the driving method comprising: resetting the photoelectric convertor of the pixel in a second row, which is different from a first row, among the plural rows during a period in which the pixel in the first row among the plural rows is being selected as a pixel to output the optical signal; and canceling the reset of the photoelectric convertor of the pixel in the second row in a period other than the period in which the A/D converting unit converts the optical signal of the pixel in the first row into the digital signal.
 2. The driving method of the image pickup device, according to claim 1, wherein the A/D converting unit further includes a sample-and-hold circuit for sampling the optical signal and maintaining the optical signals; the A/D converting unit converts the optical signal maintained in the sample-and-hold circuit into the digital signal, and a period other than the period in which the A/D converting unit converts the optical signal of the pixel in the first row into the digital signal is a period other than the period in which the sample-and-hold circuit samples the optical signal of the pixel in the first row.
 3. The driving method of the image pickup device, according to claim 1, wherein each of the plurality of pixels includes: a single micro lens; a first photoelectric convertor and a second photoelectric convertor for respectively generating charge using a light transmitted through the single micro lens; an input node to which the charge from the plurality of photoelectric convertors is transferred; and an amplification transistor for outputting, as the optical signals respectively, a first optical signal based on the charge of the first photoelectric convertor and a second optical signal based on the charge in which the charge of the first photoelectric convertor and the charge of the second photoelectric convertor are added, the A/D converting unit sequentially converts the first optical signal and second optical signal of the pixel in the first row into digital signals, and the reset of the photoelectric convertor of the pixel in the second row is canceled in a period other than the period in which the A/D converting unit converts the second optical signal of the pixel in the first row into the digital signal.
 4. The driving method of the image pickup device, according to claim 2, wherein each of the plurality of pixels includes: a single micro lens; a first photoelectric convertor and a second photoelectric convertor for respectively generating charge using a light transmitted through the single micro lens; an input node to which the charge from the plurality of photoelectric convertors is transferred; and an amplification transistor for outputting, as the optical signals respectively, a first optical signal based on the charge of the first photoelectric convertor and a second optical signal based on the charge in which the charge of the first photoelectric convertor and the charge of the second photoelectric convertor are added, the A/D converting unit sequentially converts the first optical signal and second optical signal of the pixel in the first row into digital signals, and the reset of the photoelectric convertor of the pixel in the second row is canceled in a period other than the period in which the A/D converting unit converts the second optical signal of the pixel in the first row into the digital signal.
 5. The driving method of the image pickup device, according to claim 3, wherein the reset of the photoelectric convertor of the pixel in the second row is canceled in a period other than the period in which the A/D converting unit converts the second optical signal of the pixel in the first row into the digital signal or the period in which the A/D converting unit converts the first optical signal of the pixel in the first row into the digital signal.
 6. The driving method of the image pickup device, according to claim 3, wherein the reset of the photoelectric convertor of the pixel in the second row is canceled in a period other than the period in which the A/D converting unit converts the second optical signal of the pixel in the first row into the digital signal, and in a period in which the A/D converting unit converts the first optical signal of the pixel in the first row into the digital signal.
 7. The driving method of the image pickup device, according to claim 3, wherein the reset of the photoelectric convertor of the pixel in the second row is canceled in a period other than the period in which the A/D converting unit converts the second optical signal of the pixel in the first row into the digital signal at a timing to end a transfer of the charge from the first photoelectric convertor to the input node in the first row.
 8. The driving method of the image pickup device, according to claim 5, wherein the reset of the photoelectric convertor of the pixel in the second row is canceled in a period other than the period in which the A/D converting unit converts the second optical signal of the pixel in the first row into the digital signal and at a timing to end a transfer of the charge from the first photoelectric convertor to the input node in the first row.
 9. The driving method of the image pickup device, according to claim 6, wherein the reset of the photoelectric convertor of the pixel in the second row is canceled in a period other than the period in which the A/D converting unit converts the second optical signal of the pixel in the first row into the digital signal and at a timing to end a transfer of the charge from the first photoelectric convertor to the input node in the first row.
 10. The driving method of the image pickup device, according to claim 1, wherein each of the plurality of pixels includes: a single micro lens; a first photoelectric convertor and a second photoelectric convertor for respectively generating charge using a light transmitted through the single micro lens; an input node to which the charge from the plurality of photoelectric convertors is transferred; and an amplification transistor for outputting, as the optical signals respectively, a first optical signal based on the charge of the first photoelectric convertor and a second optical signal based on the charge in which the charge of the first photoelectric convertor and the charge of the second photoelectric convertor are added, the A/D converting unit sequentially converts the first optical signal and second optical signal of the pixel in the first row into digital signals, the A/D converting unit further includes a sample-and-hold circuit for sampling the optical signal and maintaining the optical signal, the A/D converting unit converts the optical signal maintained in the sample-and-hold circuit into the digital signal, and the reset of the photoelectric convertor of the pixel in the second row is canceled in a period other than the period in which the A/D converting unit converts the second optical signal of the pixel in the first row into the digital signal or the period in which the sample-and-hold circuit samples the second optical signal of the pixel in the first row.
 11. The driving method of the image pickup device, according to claim 10, wherein the reset of the photoelectric convertor of the pixel in the second row is canceled in a period other than the period in which the A/D converting unit converts the second optical signal of the pixel in the first row into the digital signal, the period in which the sample-and-hold circuit samples the second optical signal of the pixel in the first row, the period in which the A/D converting unit converts the first optical signal of the pixel in the first row into the digital signal, or the period in which the sample-and-hold circuit samples the first optical signal of the pixel in the first row.
 12. The driving method of the image pickup device, according to claim 10, wherein the reset of the photoelectric convertor of the pixel in the second row is canceled in a period other than the period in which the A/D converting unit converts the second optical signal of the pixel in the first row into the digital signal or a period in which the sample-and-hold circuit samples the second optical signal of the pixel in the first row, and in the period in which the sample-and-hold circuit samples the first optical signal of the pixel in the first row.
 13. The driving method of the image pickup device, according to claim 10, wherein the reset of the photoelectric convertor of the pixel in the second row is canceled in a period other than the period in which the A/D converting unit converts the second optical signal of the pixel in the first row into the digital signal or the period in which the sample-and-hold circuit samples the second optical signal of the pixel in the first row, and at a timing to end a transfer of the charge from the first photoelectric convertor to the input node in the first row.
 14. The driving method of the image pickup device, according to claim 1, further comprising an amplifying circuit configured to output a signal which is an amplified optical signal, wherein the optical signal to be converted into the digital signal by the A/D converting unit is a signal amplified by the amplifying circuit.
 15. The driving method of an image pickup device, according to claim 1, wherein the photoelectric convertor of the pixel in the second row is kept to be reset during a period between a start and an end of the A/D conversion of the optical signal of the pixel in the first row by the A/D converting unit, and the reset of the photoelectric convertor of the pixel in the second row is cancelled after the end of the A/D conversion.
 16. An image pickup device comprising: a plurality of pixels configured to be arranged in plural rows and plural columns, respectively include a photoelectric convertor for generating charge, and respectively output an optical signal based on the charge; a plurality of A/D converting units configured to be provided corresponding to the plural rows respectively and convert the optical signal into a digital signal; and a vertical scan circuit configured to perform a shutter scan for resetting the respective photoelectric convertors of the plurality of pixels row by row, and a read out scan for outputting the optical signals row by row from the respective plurality of pixels, wherein the vertical scan circuit resets the photoelectric convertor of the pixel in a second row, which is a different from a first row, among the plural rows in the shutter scan during a period in which the vertical scan circuit is selecting the pixel in the first row among the plural rows as a pixel to output the optical signal in the read out scan, and cancels the reset of the photoelectric convertor of the pixel in the second row in a period other than a period in which the A/D converting unit is converting the optical signal of the pixel in the first row into the digital signal.
 17. The image pickup device according to claim 16, wherein the photoelectric convertor of the pixel in the second row is kept to be reset during a period between a start and an end of the A/D conversion of the optical signal of the pixel in the first row by the A/D converting unit, and the reset of the photoelectric convertor of the pixel in the second row is cancelled after the end of the A/D conversion.
 18. An image pickup system that comprises an image pickup device and a signal processing unit for generating an image by processing a signal output from the image pickup device, the image pickup device including: a plurality of pixels configured to be arranged in plural rows and plural columns, respectively include a photoelectric convertor for generating charge, and respectively output an optical signal based on the charge; a plurality of A/D converting units configured to be provided corresponding to the plural rows respectively and convert the optical signal into a digital signal; and a vertical scan circuit configured to perform a shutter scan for resetting the respective photoelectric convertors of the plurality of pixels row by row, and a read out scan for outputting the optical signals row by row from the respective plurality of pixels, wherein the vertical scan circuit resets the photoelectric convertor of the pixel in a second row, which is a different from a first row, among the plural rows in the shutter scan during a period in which the vertical scan circuit is selecting the pixel in the first row among the plural rows as a pixel to output the optical signal in the read out scan, and cancels the reset of the photoelectric convertor of the pixel in the second row in a period other than a period in which the A/D converting unit is converting the optical signal of the pixel in the first row into the digital signal. 